Storing md5 hash of a password in database and comparing it
$userName=strip_tags($userName);
  $pass=strip_tags($pass);

  $userName= htmlentities($userName, ENT_QUOTES, 'UTF-8');
  $pass= htmlentities($pass, ENT_QUOTES, 'UTF-8');


  $userName=mysql_real_escape_string($userName);
  $pass=mysql_real_escape_string($pass);


   $salt = 'SHIFLETT';
   $password_hash = md5($salt . md5($pass.$salt));

function validateLogin($user_name, $pass)
   {
  $userName=strip_tags($userName);
  $pass=strip_tags($pass);

  $userName= htmlentities($userName, ENT_QUOTES, 'UTF-8');
  $pass= htmlentities($pass, ENT_QUOTES, 'UTF-8');


  $userName=mysql_real_escape_string($userName);
  $pass=mysql_real_escape_string($pass);


   $salt = 'SHIFLETT';
   $password_hash = md5($salt . md5($pass.$salt));

   $result=mysql_query("SELECT COUNT(*) AS Result FROM users WHERE user_name='$user_name' AND pass='$password_hash'");

   mysql_close();

   if($row=mysql_fetch_array($result))
   {
       if($row['Result']>0)
       {
           echo "Login successful";
       }
       else
       {
           echo "Login unsuccessful";
       }
   }
   }

function hashPassword($str)
{
        return hash("sha512", $str . "salt");
}

$password_hash = hashPassword($_POST['password']);
$username = mysql_real_escape_string($_POST['username']);

mysql> create table users (
-> id int primary key auto_increment,
-> username varchar(20),
-> password char(128));

$check = "select id from users where username = '$username' and password = '$password_hash'";
$result = mysql_query($check);

if(mysql_num_rows($result))
{
    echo "<p>Login was successful!</p>n";
}

$pass=mysql_real_escape_string($pass);